Field
Apparatuses and methods consistent with exemplary embodiments relate to improving safety (improving stopping function of a reactor) of a protection system for a nuclear power plant, and more specifically, to improving a stopping function of a reactor of the protection system in which duplexed controllers independent from each other are disposed, and operation processing results of the duplexed controllers are combined in a particular manner. Thus, single point vulnerability (SPV) of the protection system is removed, and response to a common cause failure (CCF) may be provided.
Description of the Related Art
Nuclear power plants refer to power plants that generate electricity by turning a turbine generator with steam that is generated by boiling water with energy generated through a nuclear fission chain reaction. In an atomic nucleus composed of protons and neutrons, enormous energy is released when the nucleus is divided into free particles. Nuclear power plants using the above feature correspond to an optimal power source capable of obtaining significant energy even with very small amounts of fuel. In many countries, nuclear power plants are used to produce electricity.
However, in nuclear power plants, since the use of nuclear power is accompanied by a very high risk, it is necessary to control many safety devices and hire experts having advanced training.
Protection systems perform functions of monitoring a state of a nuclear steam supply system (NSSS), stopping a nuclear reactor when monitored process parameters reach safety system preset values, and mitigating the effects of accidents.
SPV refers to shutdown inducing elements of a nuclear reactor or a turbine due to a failure of a single device. Conventionally, places in which a number of SPVs occurs may exist within currently operating nuclear power plants. From among these, the number of SPVs of a reactor protection system of operating nuclear power plants built in the 1980s is about 70 to 90. These SPVs are caused by various analog equipment of the reactor protection system which is not multiplexed.
CCFs refer to a situation where simultaneous failures occur in various devices due to a common cause. When a CCF occurs in the protection system, it may seriously affect the protection system's performance of safety functions.
A representative example to easily understand CCF is Y2K (Millennium Bug) which was problematic in 1999. This refers to a phenomenon where it was determined that a computer may not recognize the year 2000 and thus may malfunction when that time occurs. However, in case of this problem, the cause of the problem was eliminated in advance through advance preparation, and only some errors occurred in some fields.